But even at peak production, the analysis said, the United States would still have to import two-thirds of its oil, as opposed to an expected 70 percent if the refuge's oil remains off the market.

At the same time, the report said new Alaska production would stem the expected dramatic decline in domestic production and extend the economic life of the Alaska oil pipeline as production from other North Slope areas declines significantly.

But even the additional domestic production would not be enough to overcome increased demand, meaning continued heavy reliance on imports, said the energy agency. The United States imports about 56 percent of the oil it consumes.

Congress has grappled for years over whether to allow oil companies access to the Alaska refuge's 1.5 million acre coastal plain, which is believed by geologists to harbor about 10.4 billion barrels of crude.

Last year the House, citing the need for more domestic oil to ease the reliance on imports, gave a green light to drilling in the refuge. The Senate refused to go along.

Many Senate Democrats, joined by a handful of moderate Republicans, repeatedly have blocked pro-drilling legislation, arguing the refuge would be harmed ecologically.

The coastal plain includes calving areas for caribou and is home to polar bears and other wildlife, as well as being a stopover for an annual migration of millions of birds.

Both sides in the refuge issue likely will use the latest Energy Information Administration report as ammunition in the next round of debate over energy legislation in Congress.

The agency's study also noted the importance of the refuge's oil to Alaska.

Without the refuge's development, oil flowing from the North Slope will fall to 500,000 barrels a day — half of current levels — by 2025, and approach levels where the pipeline may no longer be economical to operate, the report said.

With the refuge's 876,000 barrels a day, the reliance on imports would drop to 66 percent of domestic consumption, said the analysis. And the study said it would likely have little impact on world oil prices — perhaps reducing the price by 30 to 50 cents a barrel if prices were in the $27-a-barrel range.

James Kendell, one of the authors of the study, said the refuge would add to domestic production but "when you're talking of a world oil market of over 75 million barrels a day, adding 900,000 barrels by 2025 is a drop in the bucket."